Anatomy of a Running Shoe

by Super Dave, Industry Expert

Materials
Shape

Shoe Materials:
A running shoe is made up of three parts: the upper, the midsole and the outsole.

1. Upper: Holds the foot in place, protects the foot from rocks and dirt, has synthetic leather for durability, mesh for breathability and reflective material for safety.

2. Midsole: The most important part of shoe. There are three materials that make up the midsole:

EVA: Lightweight, foam-based cushioning.

Dual-Density EVA: When you double the density of something it gets stronger, firmer and heavier (twice the mass in the same amount of space).  The dual-density EVA is called a "medial post".  'Medial' because it is on the inside of the shoe and 'post' because it has a beginning and an end. The length of the post determines the amount of control.

Polyurethane: Very durable cushioning. More durable/stable than EVA and weighs more than EVA.

*New forms of EVA or combinations of EVA and rubber midsoles are being developed at increasingly faster rates. These new foams are lighter and provide you with more durability. Look for brand name foams like Mogo, Solyte, Acteeva and others.

3) Outsole: Has tread for traction, flex grooves for flexibility and protects from dirt/rocks. The outsole is made of two materials:

Carbon Rubber: The most durable (same material as tires).

Blown Rubber: Lighter, more flexible and more cushioned, but not as durable.
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Get in Shape with Shoe Shape
Imagine a line running along the center of each of your feet from heel to toe. Looking down at your feet, these lines would probably be gentle arcs similar to parentheses¿ (). This is because feet are not perfectly straight like you might think, but have some degree of curve to them. Realizing this, shoe manufacturers make shoe models in shapes from almost completely straight to curved and points in between.

Shoe shape ties in with the shoe category: the straighter a shoe is the more stable it is. The shoe acts like a "steering wheel", guiding your foot in the direction of the curve of the shoe. Here's how it works:

1. Straight: Shape found in motion control shoes built for overpronators.

2. Semi-Curved: Shape found in stability shoes and most neutral shoes.

3. Curved: Shape found in lightweight neutral shoes for faster runners.

As you can see, the shape of the shoe actually helps it do what it does! Plus, these shapes generally match the shape of the feet in each of these shoe categories. And the fit will always be better when the shape of the shoe matches the shape of your foot.
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